Remove types-attrs from the typing env dependencies.

It's incorrect, and attrs has its own typing annotations.

From https://pypi.org/project/types-attrs/:

    Note: The attrs package includes type annotations or type stubs
    since version 18.2.0. Please uninstall the types-attrs package if
    you use this or a newer version.

Author: Julian

tox.ini

@@ -87,9 +87,10 @@ commands =
 [testenv:typing]
 skip_install = true
 deps =
+    # FIXME: Why are we repeating dependencies here?
+    attrs
     mypy
     pyrsistent
-    types-attrs
     types-requests
 commands = {envpython} -m mypy --config {toxinidir}/pyproject.toml {posargs} {toxinidir}/jsonschema